It is known to provide a glass plate or glazing (these terms are used interchangeably herein) with a frame-like polymer profile. For instance such profiles have been applied directly to a glass surface by an extrusion die whereby the profile is extruded in a final shape as it is applied. With the use of certain known methods, the glass surface is first prepared for increased adhesion to the profile. U.S. Pat. Nos. 4,581,276, 4,704,175, 4,938,521, and 4,933,032 as well as U.S. application Ser. Nos. 084,863 and 08,867 filed on Aug. 13, 1987 and U.S. application Ser. No. 314,302 filed on Feb. 23, 1989, the disclosures of which are hereby incorporated herein by reference, disclose products, processes and apparatus as described above.
Polymer profiles may be extruded onto a glazing in a final shape and thereafter fully cured for increased hardness. Extruded profiles affixed to a glass surface may, for example, be used as an intermediate body to which an adhesive bead is applied during the assembly of automotive windows, wherein the adhesive bead bonds the glass to a corresponding frame. In this regard, a profile may advantageously be contoured so as to have a channel-like cross section for receiving and retaining such an adhesive bead. Profiles may also be designed to incorporate a boundary web to limit the spread of adhesive from the profile towards a center portion of the glazing wherein the adhesive would interfere with the transparency of the glass. Extruded profiles may also incorporate a lip, i.e. an extension of extruded polymer, parallel to and extending beyond the peripheral edge of the glazing. Such a lip may serve to aid in positioning the glazing within a frame during assembly and also serve to close a gap which occurs between the circumferential periphery of the glazing and a frame flange into which the glazing is affixed.
It is possible for an extruded profile to simultaneously fulfill all the functions described above. An example of such an extruded profile has a "U"-shaped profiled portion with a relatively wide base surface and a lip-like portion projecting outwardly beyond the plate's edge. The wide base serves as an intermediate body for placement and retention of an adhesive bead, while the "U"-shaped profiled portion serves as a boundary web preventing the spread of adhesive from the profile toward the center portion of a glass plate where, as noted above, the adhesive would otherwise interfere with the transparency thereof. Additionally, the lip-like portion serves to initially position and center a window during assembly, and as a decorative cover filling the gap between a circumferential peripheral edge of the glazing and a frame flange within which the glazing is affixed. Glass plates pre-equipped with such a multi-purpose extruded polymer profile are increasingly used in practice (see, e.g., Karl Heinz Brueck: "Fahrzeugverglasung" Verlag Vieweg, 1990).
In processes which provide an application of extruded pre-shaped polymer profile directly onto the surface of a glazing, an extrusion die is located proximate to, and passed circumferentially along a peripheral edge of the glazing. With the aid of known extrusion dies, it is possible to produce a uniform extruded profile even in profiles exhibiting a complex cross-sectional shape, provided that the path of the die is roughly linear.
In prior art devices used for this purpose, as a die head of a profile extrusion apparatus moves along the peripheral edge of a glazing, a calibrated opening in the die head extrudes a contoured polymer profile onto the edge. The calibrated opening has an inner portion, and an outer portion located adjacent and contiguous with the inner portion.
As used in this specification, the terms "outer" or "outward" and the terms "inner or inward") refer to a relative position of two objects, or portions thereof, in relation to their proximity to a point located in the center of a glass plate which is to receive a polymer profile. The "outer" object, or portion thereof is always distal to the center of the glass in comparison with a more medially positioned "inner" object or portion of an object. When these terms are used to describe parts of a moving die head, they refer to relative positions of parts located within the die head when it is located in a working position along the peripheral edge of a glazing.
The inner and outer portions of the calibrated openings of the prior art devices described above extrude corresponding inner and outer portions of the profile. As profile is applied to the glazing along roughly linear portions of the glazing's peripheral edge, the circumferential distance traveled about the peripheral edge of the glazing by the inner and outer portions of the calibrated opening would be the same for both portions, and thus the proper extrusion rate necessary to provide a uniform cross section of an inner and outer portion of profile would remain constant for each portion while traversing a linear track.
However, at the corners of the glazing, or at curved sections thereof, the outer portion of the calibrated opening must traverse a greater distance than the inner portion. Therefore, in corners or curved areas, a rate of extrusion of profile equal to the rate of extrusion at linear areas will not yield a uniform cross section of a profile since the outer portion must traverse a greater distance at these locations. That is, at corners and curved areas, the outer portion of the calibrated opening will simply not extrude a sufficient amount of profile so as to cover the distance traversed. Rather, the outer section of the calibrated orifice will produce an outer portion of profile exhibiting distortion and insufficient cross section. Conversely, if the extrusion rate at the outer portion of the calibrated orifice is raised sufficiently to produce a uniform cross-section at curved areas or corners, this same rate will be excessive as to the extrusion deposited by the outer portion of the calibrated orifice at linear portions of the peripheral edge.
Moreover, as the radius of the glazing's curved areas or corners decrease, i.e., as the curvature of corners or curved areas becomes more acute, the disparity between the distance traveled circumferentially by the inner and outer portions of the calibrated opening increases, causing a disparity in the extrusion rates required to obtain a profile with uniform and sufficient inner and outer cross-section. This disparity becomes even more pronounced in the case of profiles including a radially extended outward directed lip-like portion.
Extrusion die devices as known in the prior art have therefore been limited in that they have not been able to produce a profile with a uniform cross section at curved peripheral edges or corners of a glazing. Although process parameters such as temperature, viscosity, and pressure of polymer delivery have been adjusted to bring about improvements, these parameters can only be varied within narrow limits before the adjustments themselves cause additional problems.
What is needed is a die extrusion apparatus for applying a polymer profile circumferentially to a peripheral area of a glazing which applies a profile exhibiting a substantially uniform cross section to the peripheral edge, including curved sections and corners thereof.